go: lex.sx — raw string literals (backtick) + 9 tests [nothing]

Adds Go raw string literals per Go spec § String literals:
backtick-delimited, no escape processing, may span multiple
lines, '\r' chars discarded from the value.

gl-read-raw-string! mirrors gl-read-string! but skips escape
handling and the \r filter. scan! routes the leading backtick
to it; emits "string" type (same as interpreted strings — no
need to distinguish at parse/type time).

lex 123/123.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

plans/go-on-sx.md

@@ -143,11 +143,13 @@ Progress-log line → push `origin/loops/go`.
       ident/int/string/rune/{break,continue,fallthrough,return}/{++,--,),],}}.
 - [x] Float / imaginary literals (decimal floats: `3.14 .5 1. 1e10 1.5e-3`;
       imag: `2i 3.14i 1e2i`; hex floats `0x1.fp0` deferred)
-- [ ] Raw string literals `` `...` ``
+- [x] Raw string literals `` `...` `` (multi-line, no escape processing,
+      `\r` stripped per Go spec § String literals; same `"string"` type
+      as interpreted strings)
 - [x] Hex/octal/binary integer literals (0x… 0o… 0b…) + underscores
       (legacy 0123 octal also accepted; consumes lex-hex-digit?)
 - [ ] Full operator set audit (47 distinct per Go spec)
-- **Acceptance:** lex/ suite at 50+ tests. Current: 114/114.
+- **Acceptance:** lex/ suite at 50+ tests. Current: 123/123.
 
 ### Phase 2 — Parser (`lib/go/parse.sx`) ⬜
 - Consume `lib/guest/core/pratt.sx` + `lib/guest/core/ast.sx`. Chisel notes
@@ -406,6 +408,12 @@ _(none yet)_
 
 _Newest first. Append one dated entry per commit._
 
+- 2026-05-27 — Phase 1 cont.: raw string literals (backtick-delimited).
+  Multi-line, no escape processing, `\r` stripped per Go spec § String
+  literals. Same `"string"` token type as interpreted strings — parsers
+  / type checkers don't need to distinguish. +9 tests, lex 123/123.
+  `[nothing]` — pure Go work; raw strings don't touch the substrate or
+  lib/guest story.
 - 2026-05-27 — Phase 1 cont.: decimal float + imaginary literals.
   `3.14`, `.5`, `1.`, `1e10`, `1.5e-3`, `2i`, `3.14i`. `gl-finish-number!`
   handles exponent + `i` suffix; `gl-read-number!` returns the type